Design of an embedded piezoceramic actuator for active control applications

The design of a piezoceramic actuators which is to be embedded in a composite structure is examined. The actuator device must: (1) include a collocated accelerometer; (2) meet certain actuation authority (force, stroke) requirements; (3) be able to survive the embedding process; and (4) have a minimal effect on structural integrity. The need to accommodate an accelerometer limits the minimum thickness of the device. To ensure that the (brittle) piezoceramic material is not broken during the embedding process, it is encased within a frame which has been designed to protect the piezoceramic from short durations of high temperature and pressure. Additionally, the frame is used to apply a compressive prestress to the piezoceramic, ensuring that the piezoceramic is protected from tensile stresses encountered in the operating environment. The output strain levels of the piezoceramic are maximized by using a co-fired stack (178 layers) oriented such that the piezoceramic is excited in the 3 - 3 direction. Because the layers of the piezoceramic stack are to be driven at high voltages, a special high power amplifier was designed which can source the current required by the actuator. The performance of the actuator alone has been tested by driving it uniaxially into a known impedance and measuring the output force and displacement at low frequency. Results form the tests and associated models are presented, which demonstrate the performance capabilities of the actuator.